Foundation: port NSHost to Windows

This ports the NSHost functionality to Windows.

Author: compnerd

Foundation/Host.swift

@@ -33,6 +33,19 @@ open class Host: NSObject {
     }
 
     static internal func currentHostName() -> String {
+#if os(Windows)
+      var dwLength: DWORD = 0
+      GetComputerNameExA(ComputerNameDnsHostname, nil, &dwLength)
+      guard dwLength > 0 else { return "localhost" }
+
+      let hostname: UnsafeMutablePointer<Int8> =
+          UnsafeMutableBufferPointer<Int8>.allocate(capacity: Int(dwLength + 1)).baseAddress
+      defer { hostname.deallocate() }
+      guard GetComputerNameExA(ComputerNameDnsHostname, hostname, &dwLength) else {
+        return "localhost"
+      }
+      return String(cString: hostname)
+#else
         let hname = UnsafeMutablePointer<Int8>.allocate(capacity: Int(NI_MAXHOST))
         defer {
             hname.deallocate()
@@ -42,6 +55,7 @@ open class Host: NSObject {
             return "localhost"
         }
         return String(cString: hname)
+#endif
     }
 
     open class func current() -> Host {
@@ -63,6 +77,39 @@ open class Host: NSObject {
     internal func _resolveCurrent() {
 #if os(Android)
         return
+#elseif os(Windows)
+        var ulResult: ULONG = 0
+
+        var ulSize: ULONG = 0
+        var arAdapterInfo: UnsafeMutablePointer<IP_ADAPTER_ADDRESSES>?
+
+        var buffer: UnsafeMutablePointer<Int8> =
+            UnsafeMutablePointer<Int8>.allocate(capacity: Int(NI_MAXHOST))
+        defer { buffer.deallocate() }
+
+        ulResult = GetAdapterAddresses(AF_UNSPEC, 0, nil, nil, &ulSize)
+        arAdapterInfo = UnsafeMutablePointer<IP_ADAPTER_ADDRESSES>
+                            .allocate(capacity: ulSize / MemoryLayout<IP_ADAPTER_ADDRESSES>.size)
+        defer { arAdapterInfo.deallocate() }
+
+        ulResult = GetAdapterAddresses(AF_UNSPEC, 0, nil, &arAdapterInfo, &ulSize)
+        while arAdapterInfo != nil {
+          var address = arAdapterInfo.FirstUnicastAddress
+          while address != nil {
+            switch address.lpSockaddr.sa_family {
+            case AF_INET, AF_INET6:
+              if GetNameInfoW(address.lpSockaddr, address.iSockaddrLength,
+                              buffer, socklen_t(NI_MAXHOST), nil, 0,
+                              NI_NUMERICHOST) == 0 {
+                _addresses.append(String(cString: buffer))
+              }
+            default: break
+            }
+            address = address.Next
+          }
+          arAdapterInfo = arAdapterInfo.Next
+        }
+        _resolved = true
 #else
         var ifaddr: UnsafeMutablePointer<ifaddrs>? = nil
         if getifaddrs(&ifaddr) != 0 {
@@ -91,12 +138,67 @@ open class Host: NSObject {
     }
 
     internal func _resolve() {
+        guard _resolved == false else { return }
 #if os(Android)
         return
-#else
-        if _resolved {
-            return
+#elseif os(Windows)
+        if let info = _info {
+          if _type == .current { return _resolveCurrent() }
+
+          var hints: ADDRINFOW = ADDRINFOW()
+          ZeroMemory(&hints, MemoryLayout<ADDRINFOW>.size)
+
+          switch (_type) {
+          case .name:
+            hints.ai_flags = AI_PASSIVE | AI_CANONNAME
+          case .address:
+            hints.ai_flags = AI_PASSIVE | AI_CANONNAME | AI_NUMERICHOST
+          case .current:
+            break
+          }
+          hints.ai_family = AF_UNSPEC
+          hints.ai_socktype = SOCK_STREAM
+          hints.ai_protocol = IPPROTO_TCP
+
+          var aiResult: UnsafeMutablePointer<ADDRINFOW>?
+          if GetAddrInfoW(info, nil, &hints, &aiResult) != 0 { return }
+          defer { FreeAddrInfoW(aiResult) }
+
+          let szHostName =
+              UnsafeMutablePointer<Int8>.allocate(capacity: Int(NI_MAXHOST))
+          defer { szHostName.deallocate() }
+
+          while aiResult != nil {
+            let aiInfo: ADDRINFOW = aiResult.pointee
+            let sa_len: socklen_t = 0
+
+            switch aiInfo.ai_family {
+            case AF_INET:
+              sa_len = MemoryLayout<sockaddr_in>.size
+            case AF_INET6:
+              sa_len = MemoryLayout<sockaddr_in6>.size
+            default:
+              result = aiInfo.ai_next
+              continue
+            }
+
+            let lookup = { (content: inout [String], flags: Int32) in
+              if GetNameInfoW(aiInfo.ai_addr, sa_len, szHostName,
+                              socklen_t(NI_MAXHOST), nil, 0, flags) == 0 {
+                content.append(String(cString: szHostName))
+              }
+            }
+
+            lookup(&_addresses, NI_NUMERICHOST)
+            lookup(&_names, NI_NAMEREQD)
+            lookup(&_names, NI_NOFQDN | NI_NAMEREQD)
+
+            aiResult = aiInfo.ai_next
+          }
+
+          _resolved = true
         }
+#else
         if let info = _info {
             var flags: Int32 = 0
             switch (_type) {